Microengineering for optical devices at the Sowerby Research Centre

The author presents an outline of some activities in the area of microengineering for optical devices. Diffractive elements operate by impressing phase changes on an incoming optical wavefront in order to provide a desired beam manipulation. Devices so far produced operate with two phase levels and were made by etching a substrate through a photoresist mask. Beamsplitters and microlens arrays have been made. Micromirror devices are arrays of small steerable mirrors. These can be made in various ways: those described are built up incorporating a sacrificial layer, which is removed at the end of processing to free the mirror. Refractive microlenses have been made in silica by sacrificial etching of photoresist lenses. These silica lenses may be made in a wider range of focal lengths and have higher transmission and greater robustness than photoresist lenses. The fabrication of each type of device is outlined, examples are shown and applications are discussed